Most memory module cards of a computer are Double Data Rate Synchronous Dynamic Random Access Memories (DDR SDRAM), which is an SDRAM with double data transmission rates. The data transmission rate is twice as fast as system time-pulse, different than SDR (Single Data Rate) which merely read/write once in a single period. The “Double” in DDR means that data is read/write twice in a single period. When the core clock rate remains the same, the transmission efficiency is double that of the SDR SDRAM.
Because of the high-frequency signals transmission, cross-talk noise interference is easily generated.